Apparatus for controlling angular positioning and stiffness modulations of joint of robotic manipulator

Abstract

The present invention provides an apparatus for controlling the angular positioning and stiffness modulations of a joint of a robotic manipulator by use of first and second motors and a control mechanisms. The first motor, preferably a direct current motor, controls angular positioning, while the second motor, preferably a servo motor, controls stiffness modulations. The angular positioning and stiffness modulations take place simultaneously, yet independently, thereby preventing interference. The first and second motors and the control mechanism are positioned within a housing. The control mechanism includes a shaft support member and threaded and non-threaded shafts. The threaded and non-threaded shafts extend from the first and second motors through threaded and non-threaded apertures, respectively, in the shaft support member to the housing where the threaded shaft is bearing mounted and the non-threaded shaft is supported in an aperture in the endwall of the housing to connect a pulley outside of the housing which is connected to a joint and link arrangement of a robotic manipulator. The shaft support member translates back and forth within the housing dependent on its position on the threaded shaft. When the shaft support member is nearer the housing endwall, the effective length of the shaft is short, the joint is stiff, effectively making the link stiff. When the shaft support member is nearer the shaft connection end of the motors, the effective length of the shaft is longer, the effective spring is soft, effectively making the actuator and link soft.

We claim: 
     
       1. An apparatus for controlling the angular positioning and stiffness modulation of a joint of a robotic manipulator comprising: a housing;   means positioned within said housing for controlling said stiffness modulations of said joint of said robotic manipulator;   means positioned within said housing for controlling said angular positioning of said joint of said robotic manipulator;   a threaded shaft connected to said means for controlling said stiffness modulations;   a shaft connected to said means for controlling said angular positioning; and   a shaft support means having an aperture and a threaded aperture therethrough for receiving said shaft and said threaded shaft, respectively, in order for said shaft support means to translate back and forth on said shaft due to the positioning of said shaft support means on said threaded shaft.   
     
     
       2. The apparatus as in claim 1 wherein said means for controlling said stiffness modulations is a direct current motor. 
     
     
       3. The apparatus as in claim 2 wherein said means for controlling said angular positioning is a servo motor. 
     
     
       4. The apparatus as in claim 3 wherein said threaded shaft extends from said means for controlling stiffness modulations to a bearing mounted position on an endwall of said housing and said shaft extends from said means for controlling angular positioning through an opening in said endwall of said housing. 
     
     
       5. The actuator as in claim 4 wherein said threaded shaft is self locking in order for said shaft support means to be locked into position on said threaded shaft. 
     
     
       6. The actuator as in claim 5 wherein said direct current motor and said servo motor each have a first end and a second end wherein said motors are positioned within said housing directly beside each other so that said first ends of each of said motors is placed directly against a first end of said housing to thus create a chamber between said second ends of said motors and a second end of said housing. 
     
     
       7. The actuator as in claim 6 wherein said threaded shaft extending from said direct current motor to said second end wall of said housing and said shaft extending from said servo motor through said aperture in said housing each are contained in said chamber of said housing. 
     
     
       8. The actuator as in claim 7 wherein said pulley is connected to a joint and link arrangement such that when a deflecting torque is placed on said link, said shaft attached to said pulley is capable of back and forth movement within said aperture in said housing. 
     
     
       9. The actuator as in claim 8 wherein said first ends of each of said direct current and servo motors have wires extending therefrom, said wires extending through an aperture on said first end wall of said housing for connection to a power source. 
     
     
       10. The actuator as in claim 9 wherein said wire extending from said direct current motor is for electrical connection to an outlet supplying an approximate 0 to 12 volts of direct current energy. 
     
     
       11. The actuator as in claim 10 wherein said wire extending from said servo motor is for electrical connection to a generator which supplies energy in pulses. 
     
     
       12. A method of actuating a robotic manipulator comprising the method steps of: providing a robotic manipulator with an angular positioning and stiffness modulating actuator having two motors means disposed within a housing, wherein one of said two motor means is a direct current motor means for controlling stiffness of a joint of said robotic manipulator and the other of said two motor means is a servo motor means for controlling angular positioning of said joint of said robotic manipulator;   angularly positioning said joint of said robotic manipulator;   modulating said stiffness of said joint of said robotic manipulator simultaneously with said angular positioning step; and   positioning a shaft support means on a self locking threaded shaft in order to control said angular position of said joint.   
     
     
       13. The method as in claim 12 wherein the method step of positioning said shaft support means further comprises positioning of said support shaft means so that said shaft has a short effective length in order to be stiff. 
     
     
       14. The method as in claim 13 wherein the method step of positioning said shaft support means further comprises positioning of said support shaft means so that said shaft has a long effective length in order to be soft. 
     
     
       15. An apparatus for controlling the angular positioning and stiffness modulations of a joint of a robotic manipulator comprising: a housing;   means positioned within said housing for controlling the stiffness of said joint of said robotic manipulator;   means positioned within said housing for controlling angular positioning of said joint of said robotic manipulator; and   a control means positioned within said housing for simultaneously, yet independently controlling angular positioning and stiffness modulations of said joint of said robotic manipulator.   
     
     
       16. The apparatus as in claim 15 wherein said control means comprises: a shaft support means;   a shaft; and   a threaded shaft.   
     
     
       17. The apparatus as in claim 16 wherein said means for controlling stiffness modulations is a direct current motor. 
     
     
       18. The apparatus as in claim 17 wherein said means for controlling angular positioning is a servo motor. 
     
     
       19. The apparatus as in claim 18 wherein said means for controlling stiffness modulations is positioned within said housing so that a first end of said servo motor is adjacent a first end wall of said housing and a second end of said first motor means is a distance away from a second end wall of said housing. 
     
     
       20. The apparatus as in claim 19 wherein said means for controlling angular positioning is positioned within said housing adjacent said servo motor so that a first end of said direct current motor is adjacent a first end wall of said housing and a second end of said first motor means is a distance away from a second end wall of said housing. 
     
     
       21. The apparatus as in claim 20 wherein said threaded shaft extends from said second end of said direct current motor to a bearing mounted position on said second endwall of said housing and said shaft extends from said second end of said servo motor through an opening in said second endwall of said housing.